EXTENSION OF THE TELEPHONE SYSTEM TO SHIPS 179 



operation of telephone circuits to ships and must be regarded as full 

 of promise for the extension of telephone service to the highways 

 of the sea. 



Tests of Three-Channel Operation 



Of course, any comprehensive ship-to-shore radio telephone system 

 must be capable of establishing a number of telephone connections 

 from a common land station to a number of ships. The Deal Beach 

 experiments, therefore, had as one of their objectives the trying out 

 of multi-channel operation. These tests were conducted during the 

 fall of 1920 and thru January, 1921, with the S. S. Gloucester and the 

 S. S. Ontario. A third boat was simulated by a small-power experi- 

 mental set installed at the Cliffwood, New Jersey, experimental 

 station. The three channel operation is illustrated diagrammatically 

 in Fig. 23, which also shows the scheme of frequencies. The three 

 channels transmitting from Deal Beach were grouped in one frequency 

 range, spaced 30,000 cycles apart. The frequencies transmitted from 

 the ships and received at Deal Beach were grouped in another fre- 

 quency range removed 30,000 cycles from the first and having fre- 

 quency intervals likewise of 30,000 cycles. Transmitting and receiving 

 channels differing by 90,000 cycles were paired in the manner indicated 

 to form two-way circuits. While it is possible to squeeze channels 

 together more closely than this, it was not desired on the experiments 

 to go to the limit of frequency squeezing, particularly because of the 

 severe selectivity requirements imposed upon vessel equipment. 

 These frequencies represented a fair balance between technical per- 

 fection on the one hand and practically realizable conditions on the 

 other. It will be seen that the set-up was really a four-channel 

 system, with the fourth channel used on 600 meters for calling pur- 

 poses. Under these conditions three conversations were carried 

 on successfully from the single land station, two to actual ships and 

 one to a "dummy" ship at the Cliffwood experimental station. 



Equipping of S. S. "America" 



The primary development work of the ship-to-shore system was 

 carried out, as described above, in conjunction with coastal vessels. 

 Such vessels were chosen because the rapidity of their turn-round 

 gave much more frequent test periods than could be obtained by means 

 of vessels pursuing a longer route. It remained, however, to equip 

 a trans-oceanic vessel and connect her into the telephone system. 



In 1921, the development tests of ship-to-shore telephony were 

 extended to include the General Electric Company and the Radio 



